Cathode ray tube screens



June 7, 1960 H. F. CHARLOTTE 2,939,812

CATHODE RAY TUBE SCREENS Filed Dec. 2a, 1956 WARM AIR WARM NR /24 Basi 80C 2 80C 6 INVENTOR /MM*EW A TTORNE Y 2,939,812 CATHODE RAY TUBE SCREENS Hubert Frank Charlotte, 60 Stone Park Ave., Beckenham, England "Filed Dec. 28, 1956, Ser. No. 631,253

3 Claims. (Cl. 154--80) The present invention relates to cathode ray tube screens.

It has been proposed to provide recording apparatus for making records of pictures transmitted by picture telegraphy by applying the picture signals to modulate the beam in a cathode ray tube. The beam is caused to scan over a screen of insulating materal through which "pass a'substantial number of electrical conductors. Curr'ent-sen'sitive recording paper (such as that known as Teledeltos paper) is placed on the outer surface of the "screen and a conducting electrode of about the same size as the screen is placed in contact with the paper. The conducting electrode is arranged to be at a substantial positive potential relatively to the cathode of the tube. Thus, in operation as the modulated beam scans over the conductors sealed through the screen, currents of varying amplitude pass through corresponding parts of the paper whereby a recording is made.

It is an object of the present invention to provide an improved method of producing a screen for use in a cathode ray tube as hereinbefore described.

According to the present invention a method of producing a cathode ray tube screen having a matrix of conductors therethrough insulated from one another, comprises the steps of winding a substantial plurality of layers of wire on a former, each layer comprising a substantial plurality of turns, the turns of each layer being spaced from one another and adjacent layers being spaced from one another, the interstices between the turns of each layer and between the layers being filled with insulating material during winding, whereby a mass of insulating material is provided with the wire embedded therein and subsequently cutting a slice for the mass in a direction substantially perpendicular to the wires. A plurality of slices may be cut from the mass to form a plurality of screens. The insulating material may take any of various forms and may, for example, be glass or thermosetting plastic material, or a mixture of both.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which Fig. 1 is a schematic drawing of apparatus for use in producing a winding of wire embedded in insulating material,

Fig. 2 is an enlarged view of a bobbin shown in Fig. 1,

Fig. 3 shows the bobbin of Fig. 2 with a side plate removed and a Winding on the bobbin,

Fig. 4 shows a slice cut from the winding shown in Fig. 3, and

Fig. 5 shows the slice of Fig. 4 incorporated in a cathode ray tube screen.

In Fig. 1 a bath contains a thermo-setting epoxy resin mix 11 loaded with glass powder and is disposed within an air duct 12 into which air is fed at a temperature of 80 C. through an entry port 13. An exit port for the air is shown at 14. The bath contains two pigtails 15 and 16 one at each end of the bath and Kovar United States Patent O ice wire 17 of a diameter of 1 mm. is fed from a reel 18 into the mix '11 and is guided through the mix by means of the pigtails .15 and 16. The pigtails also ensure complete wettingof the wire by removal of air bubbles. By means of the hot air the mix and the wire are maintained at a temperature of C.

The wire passes outof the duct 12 through an aperture 10 :and passes into a second air duct 20. Air at 80 C. 'is fed into the duct 20 by means of a port 21 and leaves by a further port 22. Mounted for rotation in the second duct 20 is a bobbin 23 and the wire 17 is wound onto the bobbin 23 with the aid of any suitable guiding mechanism (not shown) conventionally used in coil winding. It is arranged to wind 1000 layers each of 1000 turns on the bobbin the turns of eachlay-er ibeing spaced from oneanother by & mm. and adjacent layers being spaced from one another by J mm. The speed of winding is arranged to be such that the 1000 layers are completed in hours. In other words one layer every six minutes.

During winding 21 polymerising catalyst in the form of metal-ph'enylene diarnine at a temperature of 80 C. is intermittently sprayed on to the winding by means of a spray 24 and, as the temperature of the wire, thecoating of mix on the wire and the bobbin is maintained at 80 C.fby the hot air,polymeri s'ation is effected as the work proc'e'eds. By arranging the winding rate to be one layer every six minutes the heat generated by polymerisation is able to disperse and hence the thick mass of plastic material adequately cured can be produced.

Thus any desired thickness can be built up and in this example the thickness of the plastic mass from the inside to the outside with the winding embedded therein is 10 cm. The width of the winding is likewise 10 cm. and the length is determined by the length of the centre portion of the bobbin.

Fig. 2 shows the bobbin 23 to an enlarged scale. A centre portion of core 25 is rectangular and 20 cm. long, 0.6 cm. thick and 10 cm. in width. Fixed to the core 25 are two side plates 26 and 27 the side plate having bearings 29 and being fixed to the core 25 by means of screws 30.

In Fig. 3 the bobbin is shown with the side plate 26 removed exposing the winding 31 of the wire 17 embedded in the cured plastic mass.

The winding is slid oil the core 25 and a number of slices cut from the winding each slice being transverse of the winding so that one million conductors extend from one face to the other of the slice as shown in Fig. 4 in which dots 32 represent the ends of the wires. Each slice is 10 cm. square and of course of a thickness determined byv the strength required having regard to the fact that it is to support a vacuum.

The slice of Fig. 4 may then be placed in a mould (not shown) and surrounded with a further quantity of the mix and the catalyst and cured to provide a screen as shown in Fig. 5.

The screen after being ground to required dimensions and polished is sealed into a cathode ray tube envelope.

In a further embodiment of the method making use of the same apparatus, glass is used as the insulating material in the production of a matrix of the dimensions as that already described.

Kovar wire is lightly oxidised and passed through a suspension of finely powdered glass in distilled water in the bath 10, the glass having a particle size of the order of one or two microns. Known methods, such as the pigtails 15 and 16 or V-groove are again used to ensure complete wetting and an overall, close, air-free adhesion of the glass particles to the wire. The wire is then wound on the bobbin as hereinbefore described. During winding the coil is sprayed with the suspension 3. t of finely powdered glass so that all interstices are filled between the turns and the layers of the coil. The hot air serves to evaporate the water on the wire.

To unify the glass in the coil the coil is subjected to high-frequency eddy currents, which heat the coil andfuse the glass particles together. After annealing, cross-sectional slices are taken as hereinbefore described, placed in a mould filled with powdered glass and the whole is sintered together under pressure to form a screen.

Although the screen will usually form part of the envelope and hence is required to be vacuum-tight, it may sometimes be required to mount a screen as hereinbefore described inside a cathode ray tube in which case it is not required to support a vacuum. The range of insulating materials that may be used for the screen is,

used;

therefore, increased. For example, a silicone may be I claim: r s V 1..A method of producing a cathode ray tube screen having a matrix of conductors. therethrough insulated from one another, comprising the steps of winding a each layer being spaced from one another and adjacent layers being spaced from one another, applying insulating material to said coil during the winding thereof to fill the interstices between the turns of each layer and between the layers with insulating material, whereby a a mass of insulating material is provided with the wire embedded therein, and subsequently cutting a slice from the mass in a direction substantially perpendicular to the w1res.

2. A method according to claim 1, wherein the insulating material is a thermo-setting plastic, and including the steps of initially coating the wire with a thermo-setting plastic mix at a curing temperature before the wire is wound on to the said former, spraying a curing agent onto the layers as they are wound, the curing agent also being at a curing temperature and the spraying operation being carried out in an atmosphere maintained at a curing temperature.

3. A method according to claim 1, wherein the insulating material is glass, and including the steps of initially coating the wire with a suspension of powdered glass in a liquid medium before the wire is wound onto the said former, spraying further powdered glass suspended in a liquid medium onto the coil as it is wound, evaporating the liquid medium ofi the wire during winding and subsequently heating the coil to cause fusing of the glass particles. 7

References Cited in the fileof this patent UNITED STATES'PATENTS Hardison June 5, 1956 

1. A METHOD OF PRODUCING A CATHODE RAY TUBE SCREEN HAVING A MATRIX OF CONDUCTORS THERETHROUGH INSULATED FROM ONE ANOTHER, COMPRISING THE STEPS OF WINDING A SUBSTANTIAL PLURALITY OF LAYERS OF WIRE ON A FORMER TO FORM A COIL WITH A WINDING SECTION CORRESPONDING TO THE SIZE AND SHAPE OF THE SCREEN TO BE PRODUCED, EACH LAYER COMPRISING A SUBSTANTIAL PLURALITY OF TURNS, THE TURNS OF EACH LAYER BEING SPACED FROM ONE ANOTHER AND ADJACENT LAYERS BEING SPACED FROM ONE ANOTHER, APPLYING INSULATING MATERIAL TO SAID COIL DURING THE WINDING THEREOF TO FILL THE INTERSTICES BETWEEN THE TURNS OF EACH LAYER AND BETWEEN THE LAYERS WITH INSULATING MATERIAL, WHEREBY A MASS OF INSULATING MATERIAL IS PROVIDED WITH THE WIRE EMBEDDED THEREIN, AND SUBSEQUENTLY CUTTING A SLICE FROM THE MASS IN A DIRECTION SUBSTANTIALLY PERPENDICULAR TO THE WIRES. 